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All,
We purchased a new Carbon-Kevlar #1 in mid August of this past summer, but it seemed a little long in the luff as we had a hard time getting enough luff tension. A friend and our closest competitor purchased essentially the same sail before the start of the season. We both sent our sails back to the sailmaker recently and asked him to check them out. The sailmaker confirmed that our sail was 6” longer than our competitor’s when laid flat with only moderate tension. However, when both sails were tensioned with 60 lbs, our sail was only 2” longer. The sailmaker attributed the 4” difference between tensioned and no tension to our competitor’s sail developing more “elasticity” from use. He also explained that our competitor’s sail was designed to be 2 cm (~3/4”) shorter in the luff, though he wasn’t completely clear on why this was. That still leaves a difference of ~1.25”, that the sailmaker attributed to shrinkage of our competitor’s sail. So, my questions for all you experts out there, are:
1) Does it make sense that a sail develops more “elasticity” as it ages? This is counter-intuitive to me. Usually as springs wear out, they develop less “elasticity”.
2) Does it make sense that a sail that has seen 5 months of use would shrink 1.25” more than one that has seen 1.5 months use? That seems like a big difference to me.
Your thoughts and comments would be appreciated.Hugh Morrin
Blue Zulu
MK III, #894
Nepean Sailing Club
Hugh Morrin
Blue Zulu, C&C 27 Mk III, #894
Nepean Sailing Club, www.nsc.ca/cc27
President and back-up webmaster, C&C 27 Association
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Hi Hugh,
First, answers to your questions:
1) NO!
2) NO!
Now, the details! I don't have specific knowledge or experience of the carbon/kevlar material, but have purchased (too) many laminate sails over the last fifteen years from more sailmakers than I can forget, so here are my thoughts:
I'm not sure the various measurements you've been given by your sailmaker are much help. What're the actual luff lengths when new? Now at rest? Now under "moderate tension"? Now under sixty pound tension? And why sixty pounds? Typical halyard tension in any breeze would be way higher than that, did the sailmaker use sixty because it's simple for them to measure? Not sure it provides any valid data.
I've never encountered a laminate sail where I noticed it's "elasticity" increased with age. Typical laminates shrink at varying degrees through a sail's useful life, then begin to stretch out with age and less careful use. I've not heard of two similarly constructed sails exhibiting elasticity differences as you've described, and have crewed in active one-design fleets where such a variance would be quite apparent. I guess I'm suggesting "elasticity" is a red herring the sailmaker's using to deflect attention from the fact that the sails were not built to the same dimensions (as I'd guess they should've been) and/or one of the sails was constructed poorly and/or one of the sails was built using defective laminate.
Do you and your competitor set, sail, and store your sails equally? What about the conditions he sailed in before you got your genoa in August? What I'm trying to establish is that it's kinda pointless to compare your sail to another - your concern is over the cut, shape, and durability of your own genoa, not someone elses.
So, what about your sail?
Let's start with size - did the luff length shrink sufficiently over the season to enable a full hoist? Was the sail uninterrupted at deck level, shrouds, and spreaders? How about clew position - did it match your track location?
What about shape - were you happy with the shape - draft, curves, adjustability?
And finally, what about performance? Could you match your buddy's height and speed? Is it fair to make those comparisons based on the boats' prep and crews' sailing experience?
If your concerns are based on the comparisons of the two sails and not your actual performance, set that aside and concentrate on working with what you've got.
If, on the other hand, you're struggling compared to the competition, you need some better answers from your sailmaker than "elasticity" and unexplainable dimension variances. You deserve an understandable explanation and corrective action plan, not some salesman's smoke-and-mirrors routine. Talk to the loft's head designer or owner to get a better understanding of what's happened.
So, what's the bottom line? How'd you like the new sail? How's Blue Zulu going?
Cheers,
Tal Wolf
Critical Path
1976 Mark III #632
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Hugh Morrin,
I have no experience with a kevlar fiber sail on a C+C 27 but I have plenty of experience with Kevlar reinforced sails on larger boats. C+C 40. Sydney 42, etc. In addition I am an applcation engineer for power transmission belts that use kevlar as a reinforcing member. Here is the skinny on Kevlar.
It's total elongation over it's lifetime is less than 1%. In addition Kevlar has no elastic properties. Once the fibers ar elongated the deformation is permanent. Therefore there is no "elasticity" of the sail. Kevlar does not shrink nor does it elongate under a wide temperature range. -30 F to 190 F. That is why it is used on Vbelt drives for heavy industrial machines.
Therefore, I would guess that if the sailmaker is giving you an honest opinion that the sail is changing luff lengths over its lifetime then he has to be refferring to the fabric portion of the sail, not the reinforceing members. If that being the case they made a sail out of strong material and glued it together incorrectly not taking advantage of the strength of the reinforcing fibers.
My experience with plastic go fast sails is that they look they same the first day you set them, every day you set them until UV takes out the fabric and you end up with the luff, leach and foot of the sail with noting in between. (Rather cool to see a main sail explode in 30 knot breeze. Noting left but the batten pockets hanging from the leach. Race 4 Chicago Noods. And we told the owner to put the dacron main up that day at the dock).
Once you get a good plastic sail, you can slightly alter the depth with lots of mast bend for the main and halyard tension for the jib, but only so much. You can mover the draft position a limited amount with luff tensions so that is why you have to get the thing made correctly from the get go.
Finally I raced on a 1967 ish Red Line (CAl) 30 many moons ago. We got a plastic hgeadsail for the boat. In the long run a big mistake due to the fact that you can not bend the rig that much. We selected the rating at 22 knots top end for the sail. We never liked the way the thing set until one day we were racing with 20 apparent. Man did that sail look great and we were so much faster than the competitors that had been kicking our buts up to that point in time.
Therefore what did you tell the sailmaker other than make one just liek this?
Did you specify depth, draft position and wind rating? I think he either got it wrong or you haven't seen the sail under all of the possible conditions.
Good Luck.
Eric Steele
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